The most commonly used adsorbent for water contaminants is granular activated carbon (GAC). After it is used in a water treatment process, the GAC having adsorbed contaminants is either discarded or reactivated by heating the GAC to high temperatures. However, regenerating or reactivating GAC is an expensive process because of the energy costs involved in heating. Similarly, discarding used GAC is not desirable from an environmental perspective, and replacing the GAC that is discarded can be expensive. In addition, there are costs and liability associated with the transport of used GAC.
The property of cyclodextrins to form inclusion complexes with various molecules through host-guest interactions (Caliman et al., 2009, Clean 37(4-5), 277-303) has made them useful compounds for the removal of a number of contaminants from water and wastewater (Yamasaki et al., 2006, J Chem Technol Biotechnol, 2006, 81:1271-1276; Mhlanga et al., 2007, J Chem Technol Biotechnol 82:382-388; Yamasaki et al., 2008, J Chem Technol Biotechnol 83:991-997; Zhao et al., 2009, J Inclusion Phenomena Macrocylic Chem 63: 195-201). The formation of inclusion complexes with bisphenol A (BPA) has been reported in solution phase (Liu et al., 2008, Carbohydrate Research 343(14):2439-2442), and in solid phase by using (β-cyclodextrin-polymer (Wang et al., 2006, Sensors and Actuators B 114:565-572). The commonly available types of cyclodextrins are α-cyclodextrin, (β-cyclodextrin, and γ-cyclodextrin, which consist of six, seven and eight α-1,4 linked D(C)-glucopyranose units, respectively (Crini, 2005, Prog. Polym. Sci. 30 38-70). The presence of hydroxyl groups at position 2, 3, and 6 in the glucose unit can be used for structural modifications of cyclodextrins (Khan et al., 1998, Chem. Rev. 98, 1977-1996) in order to obtain insoluble derivatives of cyclodextrins (Sugiura et al., 1989, Bulletin of the Chemical Society of Japan 62(5):1643-1651; Crini, 2003, Bioresource Technology 90(2); 193-198; Girek et al., 2005, Carbohydrate Polymers 59(2):211-215; Yamasaki et al., 2008, J Chem Technol Biotechnol 83:991-997), and to immobilize them onto inorganic supports such as silica (Armstrong, 1985, U.S. Pat. No. 4,539,399; Crini et al., 1995, Chromatographia 40(5-6):296-302; Phan et al., 1999, Physical Chemistry Chemical Physics 1 (22):5189-5195; Crini et al., 1999, Chromatographia 50 (11-12):661-669; Morcellet et al., 2000, J of Inclusion Phenomena and Macrocyclic Chemistry 38 (1-4): 345-359; Phan et al., 2002, Reactive & Functional Polymers 52:117-125; Carbonnier et al., 2003, E-Polymers, article no. 004; Ponchel et al. Microporous and Mesoporous Materials 75(3):261-272 (2004), Saikia et al., 2008, Colloids and Surfaces A: Physicochemical and Engineering Aspects 329(3):177-183). The chemically bonded organic-inorganic particles combine the advantageous properties of both inorganic support (excellent mechanical strength) and bonded organic compounds (high efficiency, reproducibility, and selectivity) (Carbonnier et al., 2004, J. of Appl. Polym. Sci. 90:1419-1426).
The use of silica particles coated with (β-cyclodextrin ((β-CD) polymer for the removal of contaminants from water is described by Suri and Bhattarai (International Patent Pub. No. WO 2013/059285, which is hereby incorporated by reference in its entirety). In Suri and Bhattari, the adsorbent β-CD-coated particles can be packed in a column or bed, wherein water is allowed to flow through the column so that contaminants are adsorbed onto the β-CD adsorbent particles. Alternatively, β-CD-coated particles can be mixed with stationary water, i.e., water in a tank wherein the mixture of water and β-CD-coated particles is stirred to remove contaminants from the water. After the capacity of the β-CD-coated particles to adsorb contaminants is reached, the particles can be regenerated by treating them with an organic solvent such as methanol (see Suri and Bhattari at para [0058]). However, the use of organic solvent for regenerating β-CD adsorbent creates the need for treating or disposing of the organic solvent after the regeneration process.
Thus, there is a continuing need for a method of regenerating β-CD adsorbent after the β-CD has been used for decontaminating water. The present invention addresses this continuing need in the art.